A conventional appliance for drying articles such as a clothes dryer (or laundry dryer) for drying clothing articles typically includes a cabinet having a rotating drum for tumbling clothes and laundry articles therein. One or more heating elements heat air prior to the air entering the drum, and the warm air is circulated through the drum as the clothes are tumbled to remove moisture from laundry articles in the drum. Gas or electric heating elements may be used to heat the air that is circulated through the drum.
In a known operation, ambient air from outside is drawn into the cabinet and passed through the heater before being fed to the drum. Moisture from the clothing is transferred to the air passing through the drum. Typically, this moisture laden air is then transported away from the dryer by, for example, a duct leading outside of the structure or room where the dryer is placed. The exhausted air removes moisture from the dryer and the clothes are dried as the process is continued by drawing in more ambient air.
Unfortunately, for the conventional dryer described above, the exhausted air is still relatively warm while the ambient air drawn into the dryer must be heated. This process is relatively inefficient because heat energy in the exhausted air is lost and additional energy must be provided to heat more ambient air. More specifically, the ambient air drawn into the dryer is heated to promote the liberation of the moisture out of the laundry. This air, containing moisture from the laundry, is then exhausted into the environment along with much of the heat energy that was used to raise its temperature from ambient conditions.
One alternative to a conventional dryer as described above is a heat pump dryer. More specifically, a heat pump dryer uses a refrigerant cycle to both provide hot air to the dryer and to condense water vapor in air coming from the dryer. Since the moisture content in the air from the dryer is reduced by condensation over the evaporator, this same air can be reheated again using the condenser and then passed through the dryer again to remove more moisture. Moreover, since the air is recycled through the dryer in a closed loop rather than being ejected to the environment, the heat pump dryer can be more efficient to operate than the traditional dryer described above. In addition, the heating source provided by the sealed refrigerant system of a heat pump dryer can be more efficient than a gas or electric heater implemented in the conventional dryer.
During operation of a typical heat pump dryer, the dryer consumes power. The dryer system will heat continuously during operation. If the amount of power consumed is greater than the rate of heat transfer to the surroundings, the system will heat up. Excessive heat can lead to reduced performance and reliability. More particularly, as air circulates, the temperature of the air within the sealed loop increases. Similarly, the thermal load to the sealed refrigerant system increases. Simply put, the excess heat must go somewhere. In some instances, the thermal load may be reduced or offset by venting hot air into the ambient environment around the dryer appliance to dissipate the excess heat, e.g., to the laundry room, via air exchange. However, this may result in undesired increases in ambient temperature within a living space.
Accordingly, a heat pump dryer appliance having improved thermal energy management would be advantageous.